Subterranean drilling systems that employ downhole drilling motors are commonly used for drilling boreholes in the earth for oil and gas exploration. FIG. 1 is a schematic side cutaway view of a prior art subterranean drilling system 100. The subterranean drilling system 100 includes a housing 102 enclosing a downhole drilling motor 104 that is operably connected to an output shaft 106. A radial bearing apparatus 108 is also operably coupled to the downhole drilling motor 104. A rotary drill bit 112 that is configured to engage a subterranean formation and drill a borehole is connected to the output shaft 106. As the borehole is drilled, pipe sections may be connected to the subterranean drilling system 100 to form a drill string capable of progressively drilling the borehole to a greater depth within the earth.
The radial bearing apparatus 108 includes a stationary bearing assembly 116 that does not rotate and a rotating bearing assembly 118 that is attached to the output shaft 106 and rotates with the output shaft 106. The stationary bearing assembly 116 and rotating bearing assembly 118 each includes a plurality of bearing elements 120 that may be fabricated from polycrystalline diamond compacts (“PDCs”) that provide diamond bearing surfaces that bear against each other during use.
In operation, high-pressure drilling fluid is circulated through the drill string and power section (not shown) of the downhole drilling motor 104, usually prior to the rotary drill bit 112 engaging the bottom of the borehole, to generate torque and rotate the output shaft 106 and the rotary drill bit 112 attached to the output shaft 106.
The stresses born by the bearing elements 120 of the radial bearing apparatus 108 are extremely large. Therefore, manufacturers and users of subterranean drilling systems continue to seek cost-effective and suitable manufacturing techniques for fabricating bearing elements with a high durability.